Purification of sulphonic salts



May 11, 1948. c, CARTER Y 2,441,258

PURIFICATION OF SULPHONIG SALTS Filed Jan. 8, 1945 2 Sheets-Sheet 1CRUDE'METAL SULFONATE NlTRO-PARAFFIN SOLVENT CONTAINING NYDROCARBON OILPREFERABLY NlTRO -PROPANE CONTACTED AT ELEVATED TEMPERATURE PREFERABLYAT I40 r= OIL-FREE SULFON ATE on. 5OL\IENT COHT|\\N|NG SOLVENT M R E lCOOLED o DISTILLATION PREFERABLY snow 60 F OIL- FREE RECOVERED O\L.-LAYER SOLVENT LAYER suLFoHATE SOLVENT CONTA\N\NG CONTMNING (roa az-usz)son: sown-msoms om (SUITABLE row. IE-USE) i s sowem) D\ST\LLATIONRECOVERED HYDROCARBON SOLVENT omzE-uss) INVEN TOR. JOHN c. cflfirciegMay 11, 1948. J. c. CARTER PURIFICATION OF SULPHONIC SALTS Filed Jan. 8,1945 2 Sheets-Sheet 2 0x33 Jn l M K Patented May 11,1941;

PURIFICATION OF SULPHONIC SALTS John 0. Carter, Berkeley, Calif.,asslgnor to Tide Water Associated Oil Company, San Francisco, Calif., acorporation of Delaware Application January 8, 1945, Serial No. 571,940

Claims. (Cl. 260-504) This invention relates. to the separation ofsulphonic salts from unsulphonated hydrocarbon matter which is generallypresent as a contaminant in sulphonic salts derived by conventionalprocesses, as, for example, in the salts of oil-soluble sulphonic acidsderived from petroleum. The invention provides a means whereby thecontaminating hydrocarbon matter is selectively dissolved in a propersolvent, permitting the separation of the sulphonic salt insubstantially pure form and the subsequent recovery of the hydrocarbonmatter from the solvent, all as morefully set forth in the following,description.

In the treatment of petroleum oil, and similar hydrocarbons, with strongsulphuric acid, either for purifying the oil or for the specific purposeof manufacturing sulphonic acids, there are formed sulphonic acids someof which (the socalled green" acids) dissolve in the acid sludge whileothers (the so-called mahogany acids) remain dissolved in the oil. Asgenerally practiced the mahogany acids are removed from the oil bytreatment with aqueous caustic soda, or other alkaline agent, wherebythe acids are converted to their corresponding sulphonic salt whichdissolves in the aqueous caustic soda. layer the sulphonate is usuallyrecovered by "salting out or otherwise. The sulphonic salts sorecovered, or converted to sulphonate of other desired metals by doubledecomposition, have found numerous uses in the arts, especially asdetergents, but their utility is greatly impaired by the presence ofoccluded oil which is dimcult, it not impossible, to remove by the usualmethods employed. Such oil is commonly present to the extent of fromabout 30% to 80% or" the crude sulphonic salt. I

It is the principal object of the invention to provide a means wherebycrude sulphonic salts may be separated from occluded oil or otherhydrocarbon matter.

Another object is to provide a means for re covering hydrocarbon matterfrom crude sulphonic salts in which the hydrocarbon matter is occluded.

A particular form of the invention has as an object the provision of acyclic solvent process for extracting occluded hydrocarbon matter frommetal sulphonates, in which the amount of evaporation required torecover the solvent is greatly reduced.

Other objects will be apparent as the description proceeds.

In accordance with the invention it has been .21.

After separation of the aqueous found that nitro-propane willselectively dissolve mineral oil and other hydrocarbon matter from crudesulphonic salts, permitting the sulphonic salt to be separated insubstantially oil-free condition by settling, centrifuging, orfiltration. Depending on the amount of oil present and, to a lesserextent on the exact nature of the sulphonic salt, the preferred amountof nitro-propane to be used will vary from about one to four volumes ofthe solvent for each volume of crude sulphonic salt. The solubility ofthe oil in the ,nitro-propane increases with increased temperature andfor'best results the mixture of crud sulphonate and solvent should bebrought to ya temperature of about 150 F., at which I point rapidseparation of the metal sulphonate takes place. At least the mixtureshould be heated above the point of complete mutual solu-- bility of theoil and the nitro-propane, which point, for the oils tested, is about100 F., to 110 F.

After separation of the metal sulph-onate from the nitro-propane-oilmixture (which may be satisfactorily accomplished by centrifuging,although settling or filtration may be employed if desired) the metalsulphonate will be found to contain approximately 25% of nitro-propane,

which may be removed and recovered for further use by distillation.

If desired the nitro-propane may likewise be recovered from the oil bydistillation, although it has been found advantageous to cool thenitropropane-oil mixture below the temperature oi complete solubilitywhereupon the oil separates out as a distinct phase which maybeseparated by decantation or centrifuging. 'The nitro-propane thusrecovered, though it will be found to contain some oil in solution, maybe used for the extraction of another batch of crude sulphonic salt. Theoil, containing about one percent a nitro-propane may be subjected todistillation to recover the solvent. By thus separating the oil bycooling the solvent-oil mixture, it will be seen that a substantialamount of distillation is avoided in the recovery of the solvent.

While the process may be carried on in batches, it is well adapted to acontinuous process; or, by proper interposition of surge tanks, theprocess can be conducted partly continuously and partly by batch.

The invention will be better understood by ref- I erence to the drawing,Figure 1 of which is a selfexplanatory flow-sheet showing the processingsteps. Figure 2 illustrates in diagrammatic form apparatus suitable forcarrying out continuous processing, in which crude sulphonic saltcontaining occluded oil entering through line I is .densed in condenserI and the condensed solvent is recycled to the process through line I I.

The oil-solvent solution leaving centrifuge through outlet 1 is passedthrough heat exchanger l2 and cooler l3, wherein it is cooled below thepoint of complete solubility, and enters centrifuge l4. As a result ofthe cooling in heat exchanger I2 and cooler iii the mixture is resolvedinto an oil phase and a solvent phase which, are separated from eachother in centrifuge H, the former leaving through outlet l5 and thelatter through outlet [6. The oil phase, still containing some solventin solution, is passed to still ll wherein the solvent is distilled offand the recovered oil is withdrawn through line it. The solvent vaporsare condensed in condenser I9 and recycled to the process through lineH.

The solvent phase, leaving centrifuge it through outlet l6 andcontaining some oil in solution, is recycled to the process through heatexchanger l2 and lines 20 and I l.

The recycle solvent in line H, recovered from condensers l0 and I9 andfrom line 20, is passed through heater 2| and thence through lines 3 andl to contactor 2. In heater 2! sumcient heat is supplied to insure thatthe mixture in contactor 2 is above the temperature of completesolubility of the solvent and oil. Fresh solvent may be added throughline 22 to compensate for any solvent losses in the process.

Suitable pumps P are provided to furnish the requiredflow of materialsthrough the apparatus. Preferably, vacuum is applied to stills 8 and I!by suitable means (not shown).

Either l-nitro-propane or Z-nitro-propane may be used as the solvent,the results being substantially the same, although l-nitro-propane ap-'pears to exert somewhat better solvency for the creased molecularweight, requiring substantially greater cooling than with nitro-propaneto cause separation of solvent from oil. Likewise the boiling point ofthe nitro-paraflln increases with molecular weight which makes therecovery oi solvent from the oil and from the sulphonic salts bydistillation more difficult.

As is known, the nitro-parafiins have a tendency to be explosive at thehigher temperatures, particularly in the vieinityof their boiling pointsand above. For this reason nitro-ethane, which requires highertemperatures to efiect complete 4 solution of the oil, and nitro-butaneand the higher nitro-, which require higher temperatures for theirrecovery by distillation, are less suitable for the process thanIntro-propane which is the preferred solvent. In any event care shouldbe taken in distilling these solvents and the use of vacuum or steam toreduce the boilin point is strongly recommended.

Following are examples of the process:

Example 1 1 450 parts of crude calcium mahogany sulphonate prepared fromoil-soluble petroleum sulphonic acids and containing 67% of oil werecontacted with 1000 parts of l-nitro-propane at a temperature of 140 F.Upon standing for a short time calcium sulphonate settled out as a lowerviscous layer which was then drawn of! from the upper nitro-propane-oillayer. Upon vacuum distillation of the calcium sulphonate there wererecovered 70 parts of nitro-propane and 150 parts of pure calciumsulphonate which, upon cooling, became an amber colored solid mass andwhich, upon analysis, showed an average molecular weight of 938,. Theupper layer after separation of the calcium sulphonate was cooled to 50R, which resulted in the formation of an upper oil layer and a lowersolvent layer, which were then separated. The solvent layer was found tocontain about 5% of oil and to be suitable for extracting a subsequentbatch of crude sulphonate. The oil layer was distilled to recovercontained solvent and from the distillation were recovered 30 parts ofnitro-propane and 260 parts of dark colored oil which analyzed 2% ashand 1.2% sulphur content.

Example 2 lQparts of crude sodium sulphonate derived from caustic sodaneutralization of sulphuric acid treated Coalinga lube distillate andcontaining 42% ofoccluded oil were heated with 31 parts ofl-nitro-propane to a temperature of 140 F., whereupon three layers wereformed: an upper layer (34 parts) of solvent and oil; a middle layer (14parts) of sodium sulphonate containing some solvent; and a lower layer(2 parts) consisting chiefly of inorganic salts. After separation of thethree layers, the upper layer was cooled to F., whereupon an oil layerwas formed, which was separated. Upon vacuum distillation of therecovered sodium sulphonate'and of the recovered oil there were obtained9 parts of pure sodium sulphonate (M. W. 449) and 4 parts of oil. Fourparts of oil remained in the solvent layer from the second separationmost of which could be recovered by further cooling. However,- thesolvent containing this amount of oil was suitable for subsequent use inextracting further amounts of sulphonate.

Example 3 20 parts of crude sodium sulphonate identical to that used inExample 2 were extracted with 60 parts of l-chloro, l-nitro-ethane at atemperature of F. Due to the relatively high density of thesolvent, theextracted sodium sulphonate settled out in a layer above the solventoilsolution, while the inorganic salts settled as a third layer below thesolvent-oil solution. After separation of the three layers, thesolvent-oil layer was cooled to 80 F., whereupon an oil layer was formedwhich was separated. Vacuum distillation of the oil layer and the sodiumsulphonate layer to remove contained solvent yielded products of similarquantity and nature as ob tained in Example 2.

Example 4 20 parts of crude sodium sulphonate identical to that used inExample 2 were extracted with 40 parts of 2-nitropropane underconditions similar to that used in Example 2. Similar products insimilar quantity were obtained.

The foregoing description has been directed primarily to explaining theinvention in relation to the removal of occluded oil from sulphonicsalts derived from petroleum oils, for 'which purnot, under theconditions of neutralization, formsalts. As used in the description andin the claims the term oil is intended to denote the hydrocarbon oiltogether with such dissolved impurities, if any.

I claim:

1. A method of removing oil from a. metal mahogany sulphonate havingoccluded oil as an impurity, while avoiding the need for washing with awater soluble organic solvent, which comprises treating one part ofimpure metal mahogany sulphonate with more than one part of awater-immiscible selective solvent to dissolve the oil, and thenseparating theundissolved metal sulphonate from the oil-solventsolution, said solvent being a nitro-paraflin and the temperature oftreating is in excess of the point of comm plete mutual solubility ofthe oil and solvent.

2. The method of claim 1 in which the nitroparamn has from two to fourcarbon atoms per molecule.

3. The method of claim "1 in which the nitro paraflin is a.nitro-propane and the treating temperature is above F.

4. The method of claim 1 in which the nitroparaflin is: achloro-nitro-ethane.

5. A cyclic process for extracting oil from a mahogany sulphonate whichcomprisesqtreating one part of a metal mahogany sulphate having oil asan impurity with from one to four parts oi a nitro-paraflin having fromone to four carbon atoms to the molecule at a temperature above that ofcomplete solubility of the oil and solvent, separating the resultingoil-solvent phase from the undissolved sulphonate, cooling theoilsolvent phase until an oil phase separates from the solvent and thenreturning the solvent thus diminished in oil content to treat furtherportions of impure sulphonate, thus avoiding the'distillation of thesolvent in order to recover it for re-use.

JOHN C. CARTER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS OTHER REFERENCES I Hass, Chemical Reviews," vol.32, pages 386- Y m. a

